A flux capacitor is a special device that is found in a time machine like the DeLorean in the movie 'Back to the Future.' It looks like a box with wires coming out of it. It helps the time machine travel to different times and places. The flux capacitor stores energy, like a battery, and releases it when the time machine needs it. When activated, it creates a time-warping field of energy that allows the time machine to move forward or backward in time.